1. Field of the Invention
The present invention relates to an optical pointing system, and more particularly, to an optical pointing system and method for controlling power and/or clock signal thereof, capable of adaptively varying a magnitude of power and/or a frequency of clock signal supplied according to a movement speed of the optical pointing system.
2. Description of the Related Art
FIG. 1 shows a general optical pointing system, in which the optical pointing system is composed of a light source 8, a lens 5, and an image sensor 3 in a movement sensing unit (not shown).
In FIG. 1, among reference numbers, 2 indicates a surface of a worktable, and 4, 6 and 7 indicate light.
In the optical pointing system shown in FIG. 1, the light 7 emitted from the light source 8 is reflected on the worktable surface 2, and the reflected light 6 passes through the lens 5. The light 4 passing through the lens 5 is inputted into the image sensor 3 which is located in the movement sensing unit (not shown) and is included in a CMOS (Complementary Metal Oxide Semiconductor) device.
An image of the worktable surface 2 is continuously sensed by the image sensor 3, and is outputted to a sensor circuit (not shown). The sensor circuit calculates a correlation value between currently inputted image data and previously inputted image data and a movement value, and then transmits the calculated movement value to a computer system.
FIG. 2 is a block diagram showing a conventional optical pointing system, in which the optical pointing system is composed of an optical unit 10, a movement sensing unit 20, a microcontroller 30, a power unit 40, and a clock signal generating unit 50. In FIG. 2, the movement sensing unit 20 includes an image sensor 21, an A/D converter 22 and a movement value calculator 23.
Hereinafter, functions of each of the blocks shown in FIG. 2 will be described.
The optical unit 10 is composed of a lamp, a lens and other attachments. The optical unit 10 irradiates light toward an object (for example, a surface of a worktable) through a lamp, and transmits the light reflected on the object (to the image sensor 21 via the lens. The movement sensing unit 20 calculates a movement value MOV using an optical image transmitted from the optical unit 10. The image sensor 21 receives the reflected light through the lens to sense image data. The A/D converter 22 receives an analog signal outputted from the image sensor 21 and converts the received analog signal into a digital signal. The movement value calculator 23 calculates and outputs the movement value MOV from the image data that is the output signal of the A/D converter 22. The microcontroller 30 receives the movement value MOV outputted from the movement sensing unit 20 and other external input information and transmits the received results to a computer (not shown) based on a specification required at the computer. The power unit 40 supplies required power POW of a fixed magnitude to a circuit. The clock signal generating unit 50 supplies a required clock signal CLK of a fixed frequency to each part of the circuit.
When the optical pointing system moving on the object including the worktable intends to obtain the movement value, the optical pointing system must obtain discrete image frames and then calculate the movement value through comparison and analysis between the image frames. Thus, in order to obtain a normal movement value, the following condition should be satisfied: the greater the movement speed of the optical pointing system becomes, the faster an operating speed of the circuit such as an acquisition speed of the image frame should be.
In the conventional optical pointing system as mentioned above, in order to get rid of problems when the optical pointing system operates at the fastest speed, the power and clock signal corresponding to the fastest speed are supplied fixedly. However, in the case of electrical devices, as the operating speed becomes faster, power consumption is proportionally increased as well. Further, in general, in an integrated circuit produced by a CMOS process, the operating speed is proportional to a supply voltage, while consumed power is proportional to a square of an applied supply voltage. Thus, the conventional optical pointing system undergoes undesired power consumption.